15th Feb 2024: Astro Pixel Processor 2.0.0-beta29 released - macOS native File Chooser, macOS CMD-Q fixed, read-only Fits on network fixed and other bug fixes
7th December 2023: added payment option Alipay to purchase Astro Pixel Processor from China, Hong Kong, Macau, Taiwan, Korea, Japan and other countries where Alipay is used.
At the end of February 2016 I shot M81 and M82 with my 10"F5 Newton in a 2 pane mosaic. The integration times are:
M81 Luminance 33x600 sec, RGB 12x600 sec each and Ha 13x600 sec
M82 Luminance 36x600 sec, RGB 12x600 sec each and Ha 14x600 sec
I already created the mosaic shortly after capturing the data, but now that APP is on the market I decided to reprocess the data all over again. With the workflow still fresh in my memory I thought it was a good idea to share this. I don't know if I did process it the right way (maybe there's an easier way or a better one), the main thing is I got what I wanted: a good result.
After the first night I made a set of flats, but halfway the imaging session (it took me 7 nights) somehow I had some dust particle on my sensor, so I had to make a second set of flats. I started with creating a BPM using the master dark and a set of flats. After that I created 2 sets of master flats using the master bias and the flats: one set of master flats without the dust particle and one set with the dust particle. Now the master files are complete I started calibrating the lights using the BPM, master dark and master flat. Most of the lights could be calibrated with a single master flat except the lights that were shot during the night I got the dust particle. I solved this by calibrating the lights separately and save the normalized frames. After that I loaded these frames again, without any master files present in the file list, and did the integration.
I now had 10 stacks (5 channels for each pane). First of all I did a Light Pollution Correction for each stack separately. This had to be done carefully in both the luminance stacks because there was IFN (Integrated Flux Nebula) present in these stacks, but APP did a great job.
After that I did a batch crop on both of the sets to get rid of the bad borders. I loaded all of these cropped stacks (10) and registered them again using settings for composing a mosaic. This way all of the stacks are registered the same way. To create a mosaic for each channel separately I just checked the both stacks in the file list (or unchecked the rest) and did an integration, resulting in 5 frames (one for each channel) containing both stacks. Again APP did a great job.
Finally I loaded these with the “Combine RGB” and adjusted the settings until I was satisfied, did an “Neutralize Background” and a “Star Color Calibration”. This is the result I got:
Hi Jeroen,
This is a very nice M81 & M82. Holmberg IX (satellite galaxy of M81) is visible and yes, the IFN does seem to show here and there 😉
I have made several mosaics from data of the beta team and I found by using LNC +MBB on the indivdual panels I rarely needed to remove borders of the panels leaving me with more overlap between the mosaic panels, which is always beneficial. An example from data of Yves van den Broek, part of his Barnard's Loop mosaic:
The second image is the same data as the first image but integrated with a higher degree of LNC applied (I believe 4th degree). If I didn't do this, I needed to use the first integration, which obviously needed cropping. Thanks to both LNC and MBB I was able to avoid this, leaving me with more data to compose the mosaic. So perhaps you can improve there in a future mosaic.
I think your workflow is pretty good already, the separate masterflats can indeed be dealt with, with saving the calibrated data per set of calibration frames needed like you did.
Great image !
Mabula
Hi Mabula,
thank you for the info. Old habits die hard I think. In the programs I used before APP I alway had to crop the stacks before starting the mosaic because the crummy corners and dark edges would cause problems, but APP is doing a wonderful job.
Jeroen
Excellent, thank you Jeroen 😉
Congratulations Jeroen on a very beautiful mosaic. You have some really nice details and colors look good as well. FWIW, I've used Multi Band Blending on a few of my images, and it's quite amazing how well it blends panels together.
One other suggestion...the process you used to deal with the dust particle/flat problem. Basically, I think you did everything correctly - calibrate each night's frames with appropriate calibration files. However, you mentioned that you calibrated **and** normalized them and then saved the files.
For my purposes, I usually image over many nights. I'll calibrate and save each night's subs, but I do not normalize them at that point. In that case, they would be normalized to each of the other subs taken that night (in your case normalized to all of the similar dust donut or no-dust subs). That won't hurt anything, but you want to be sure that you normalize ALL of the subs when you integrate them.
In other words, if you have one set of normalized subs and another set of normalized subs, they are not normalized to each other. If you then tried to combine them in a mosaic without normalizing again, then you could easily end up with some seams that were difficult to blend.
For this reason, my basic process is to calibrate all frames with their appropriate calibration files. Then, when I'm ready to integrate them all, I normalize and integrate.
Hope this helps,
Hi Scott and Jeroen,
Thank you Scott for your feedback.
Scott makes a good argument. It's not needed to normalise the lights per session/night.
Normalization of the data can wait until you are ready for integration of all subs 😉
Kind regards,
Mabula
